Merging a complete rewrite in another language in 9 days seems insane to me. Maybe I'm just too cautious but with something like this I'd split off as a separate binary and get some heavy use customers involved as testers first to see if it causes any unforeseen problems before slowly expanding it out.

I'd want to be pretty damn confident it won't cause any regressions before sunsetting the original codebase in favor of this one.